Reloder TS 15.5: Nullifying The Thermometer

Alliant Powder Reloder TS 15.5 is aiming to nullify your need for a thermometer as a handloader.

“See, this one goes to 11.” Why don’t they just make 10 louder?” “This one goes to 11.”

The classic exchange from This Is Spinal Tap has been referenced more times than you could count, but it immediately came to mind when I heard of the release of Alliant’s Reloder TS 15.5—“it’s 0.5 better.”

But there’s more to this new powder than just modifying Reloder 15—which is incredibly useful in cartridges like the .17 Remington, 5.56mm NATO, .22-250 Remington, .308 Winchester, .30-06 Springfield, .375 H&H Magnum, .404 Jeffery and .470 Nitro Express—and the new release needs a fair shake.

Temp Through Time

Well, let’s start with its proper name: Reloder TS 15.5. The “TS” stands for Temperature Stable, and that’s been the buzzword among the latest powder releases. Exactly how instable was our old lineup of powders? Well, there was a rule of thumb among ballisticians that became near-gospel: Every degree Fahrenheit of temperature change—up or down—from the test data temperature would either add or subtract 2 fps.

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For example, if you developed a load using good old IMR 4064 at 65 degrees Fahrenheit, and then took the load to hunt late-season caribou adventure, where the temperatures hover around 0 degrees, you could expect a velocity loss of roughly 130 fps. Take that same load to Texas in June or to Zimbabwe during October, where a thermometer reading of 100 degrees is common, and you’ll see your velocities increase by 70 fps or so.

Now, should your chosen powder charge be well within the realm of safety, that increase might not matter in the least. But, if that load is on the cusp of unacceptable pressure, when the temperatures get warmer you might find cratered primers, a sticky bolt, difficult extraction and other issues.

In a bolt-action, lever-action or single-shot rifle, the temperature fluctuation might not pose a huge issue, so long as the pressures are acceptable, and shouldn’t result in much more than an adjustment of your scope. But I’ve seen shooters bring a rifle to the range in the warmer months—after having put it away after deer season, knowing it was properly zeroed—only to find a bughole group at a different point of impact.

“My scope must’ve got bumped.” No, we’re likely seeing the effects of warmer temperatures. This is why the manufacturers are stressing the temperature stability of newer designs, and they have proven to minimize the effects of temperature swings.

Reloder TS 15.5 claims a burn rate “between Reloder 15 and 16,” but that’s a rather vague statement, as there’s an awful lot of real estate between the two. Looking at a modern burn rate chart, you’ll find that Reloder 15 sits just north of IMR 4064, and Reloder 16 sits just south of H4350. In between resides Hodgdon’s Varget BL-C (2) and H380, as well as IMR4350 and IMR4451, Winchester 748 and 760, and Alliant’s own Power Pro 2000MR and 4000MR.

Assuming a burn rate smack-dab in the middle, you’re looking at a rather versatile powder, which can serve a good number of different cartridges, from the .223 Remington and .22-250 Remington, up through the 6mm Creedmoor and 6.5 Creedmoor, to the .308 Winchester and .30-06 Springfield. Based on my experiences with the .375 H&H Magnum, I could see where Reloder 15.5 would be a natural fit.

The RL TS 15.5 is an extruded stick powder, with a rather large grain structure when compared to RL 15, looking very similar to RL 16. This shouldn’t pose an issue in the larger cases like the .30-06 and family, or the .22-250 and 6.5 Creedmoor. But for the .223 Remington, and even the .308 Winchester, compressed loads might be an issue.

That said, I had more than acceptable results in my .308 Winchester, using a 180-grain Nosler Partition (perhaps one of the finest choices for an all-around hunting bullet) and a charge of 44.7 grains of RL 15.5, sparked by a Federal GM210M primer. In my well-worn Ruger .22-250 Remington, a charge of 37.0 grains of RL 15.5 topped with a 53-grain Sierra MatchKing printed three shots in just over ½ inch at 100 yards, at a velocity of 3,690 fps.

Based upon the excellent results I’ve had over the years using RL 15, IMR 4064, IMR 4350 and H380 in the .375 H&H case—all being in that same burn rate range between RL 15 and RL 16—I thought that RL 15.5 would be a natural fit for the classic case. While there’s no published load data for the .375 H&H using the new powder, it’s apparent that the differences in most cases between RL 15 and RL 15.5 aren’t much more than 1 grain, so using the RL 15 data as a starting point is a safe plan.

Using a 285-grain Speer Grand Slam and the data from the Speer Handloading Manual Number 15, I started at 2 grains below maximum, with 67.0 grains. The Speer data tops out at 69.0 grains, and that’s where I found the accuracy/velocity combination I deemed suitable for a proper hunting load. Pushing that bullet at 2,490 fps into three-shot groups measuring just under 1-MOA, I saw an ES value of 15 fps for this load.

Made in Sweden, Reloder TS 15.5 has a de-coppering agent built into the formula to help reduce bore fouling, and it has the potential to perform equally well in hunting applications as it does in target rifles. For those fans of the 6mm cartridges—especially the .243 Winchester and 6mm Creedmoor—you might find a fast friend in RL 15.5. I think it’ll also prove that this powder might be perfectly suited to the Mauser-based cartridges like the 7×57, 8×57, .257 Roberts and more.

Will I be abandoning those proven loads I have using good old Reloder 15? Probably not. But, when working up a new load for a different bullet or for a new cartridge, RL TS 15.5 could be the powder that just might yield one of those magic combinations.

Editor’s Note: This article originally appeared in the July 2022 issue of Gun Digest the Magazine.

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